PHILADELPHIA -- The big buzz for 2019 on medication interactions is: Don't overreact to a history of penicillin allergy, Douglas Paauw, MD, of the University of Washington, said at the .
"[You have patients who] are 60-70 years old and they say, 'You know, when I was a baby, my mom told me I had a reaction to penicillin and [I should] never take it.' How many have heard that story?" said Paauw. However, "most of those are probably not real ... and most people outgrow those allergies. With that type of distant history, it's safe to go ahead and treat them."
On the other hand, "if they said, 'I was put in the ICU and intubated because I had anaphylaxis and was on a ventilator for 2 months' -- yeah, I probably wouldn't reach out to that person, or if I did anything I'd probably skin test them, but be ready to be a little more liberal about re-challenging these patients," he added. That can be done in a controlled setting in the office -- "have epinephrine ready, give the medicine, [have them] stay around for a few hours, and then go home. If you're uncomfortable with that, you can send them to the allergist ... That's where we are in 2019 with this allergy."
This can be especially helpful when a physician is considering alternatives to fluoroquinolones, according to Paauw. He gave the example of a 75-year-old man who develops a fever, chills, and a cough. He has a history of coronary artery disease, hypertension, prostate cancer, colon cancer, and an aortic aneurysm. He is allergic to amoxicillin and is currently taking atorvastatin, amlodipine, lisinopril, and aspirin, and his chest x-ray shows a right middle lobe infiltrate.
One medication that should not be prescribed to this patient is a fluoroquinolone such as levofloxacin, Paauw said. He cited a involving 1.7 million patients age 65 and older who were tracked for 15 years; in particular, fluoroquinolone prescriptions were tracked, with patients considered at risk for an allergic reaction during the course of treatment and for 30 days after. The researchers found that tendon ruptures and aortic aneurysms were significantly more likely to occur when patients took fluoroquinolones (HR [hazard ratio] 3.13 and HR 2.72, respectively, P<0.001 for both).
Due to such study results as well as an association with peripheral neuropathy and arrhythmia, the FDA has warned physicians not to prescribe fluoroquinolones for common ailments such as acute sinusitis, which is where the alternatives come in, Paauw said. "Cephalosporins are a very good option for those we [would] choose fluoroquinolones for," he said.
He discussed other adverse events associated with commonly used medications, including:
- Canagliflozin in diabetes patients. The SGLT-2 inhibitors "are great drugs ... but there are some concerns about them," Paauw said. In particular, a about canagliflozin cited an increased risk of amputation in some patients; risk factors include prior amputations, peripheral vascular disease, neuropathy, and diabetic foot ulcers. In such patients, "you should probably consider a different option," he said.
- Hydrochlorothiazide in patients with skin cancers. found that high use of hydrochlorothiazide -- 50,000 mg or more -- was associated with odds ratios of 1.29 for basal cell carcinoma and 3.98 for squamous cell carcinomas. "This is not a reason not to use thiazide diuretics, but in patients who have already had skin cancer ... we might think of alternatives," Paauw said.
- Antibiotics, corticosteroids, and other drugs in patients on warfarin. Warfarin has a long list of drugs with proven and possible interactions; "the 'possible' category is harder in some ways" because it doesn't always happen, Paauw said. "Interestingly, tramadol is recognized as having an impact on INR [international normalized ratio], with an average bump of 0.5," said Paauw. "What's hard is that it doesn't always do it, so if you have to put somebody on medications like these, bring them back in 3-4 days and re-check their INR."
found that concurrent azithromycin use bumped INR an average of .51, while trimethoprim/sulfamethoxazole (TMP/sulfa) increased it 1.76, he added. "If people are on these drugs, do they have an increased risk of [gastrointestinal] bleeding? the answer is Yes," he said. "The greatest risk is TMP/sulfa because it has the greatest anti-coagulant effect."
Oral corticosteroids also can bump up the INR numbers on warfarin patients. "This is important to know because we usually give people steroids for a short period of time, and if you happen to take the INR during that time, it's going to be really high," said Paauw. If the clinician then lowers the warfarin dose as a result of that reading, the next INR result will be really low because the patient is no longer on steroids, he said. "The bottom line is be aware of it, but don't overreact to it."